The invention is based on an apparatus for the rpm-dependent adjustment of the timing of an injection pump. Many forms of apparatus for the rpm-dependent adjustment of the timing of injection pumps in internal combustion engines, which are also known as shaft-type injection adjusters, are known. In one known apparatus (U.S. Pat. No. 3,050,964), which also defines the field of the present invention, flyweights supported on the rotating part are provided, which move outward as the rpm increases and mechanically engage an axially displaceable valve member via protrusions which effect a lever translation. The valve member in turn then enables the supply of pressure medium to an annular groove in a sliding sheath. As a result, the sliding sheath undergoes an axial displacement in accordance with the rpm and thereby simultaneously changes the adjustment angle between the rotating primary part and a secondary part connected with the primary part in a rotationally coupled manner. This change in the adjustment angle is effected by the meshing of a bevel gear on the sliding sheath with at least one of the parts thus coupled rotationally with one another.
With decreasing rpm, a restoration of the valve member to its original position takes place as the result of spring pre-stressing, and the pressure medium is carried away to a pressure medium sump. The known apparatus is complicated in design and requires a mechanical operative connection between the displacement movement of the flyweights, which is effected by rpm variation, and a valve member effecting the control of the pressure medium. As a result, taking other control variables besides the rpm into consideration is at best made more difficult. Furthermore, it cannot be precluded that at low and medium rpm levels, at which the rpm-dependent adjusting member adjustment already begins, frictional influences may occur which are not always negligible.
In another known apparatus (U.S. Pat. No. 3 258 937) for adjusting the relative angle between rotating driving and driven parts, the pressure of a pressure medium is exerted continuously upon a displaceable piston element which is in a state of operational bevel-gear engagement with at least one of the parts. However, at low rpm the position of a valve member disposed in the path of pressure medium supply is influenced by flyweights to such an extent that an outlet to the pressure medium sump is opened; this outlet is closed off only when the rpm is sufficiently high, and the axial displacement of the piston element, which is embodied like a sliding sheath, takes place counter to the pressure of a spring acting upon it, and thus the change in adjustment angle takes place as well.
Types of apparatus for the rpm-dependent adjustment of the instant of injection in internal combustion engines are also known from U.K. Pat. No. 779 657; U.S. Pat. No. 3 447 520; U.S. Pat. No. 3 718 127; and German Auslegeschrift No. 1 805 276.
In U.K. Pat. No. 779 657, pistons which are subject to the action of a pressure medium and execute opposing movements in the radial direction are provided; they act mechanically via connecting elements upon coupling parts between the driven and the driving part in such a way that an adjustment in the rotary angle is effected. The supply of pressure medium is effected in a manner controlled in accordance with rpm by means of control slides supported in the pistons; these control slides are equipped with a cast part and during operation are subjected to centrifugal forces.
In the fuel supply apparatus of U.S. Pat. No. 3 447 520, a relative angular rotation of a cam path variously determining the instant of injection takes place under the influence of a piston movable by a fluid pressure; the fluid pressure itself is picked up directly from the outlet of the feed pump, which (since the feed pump is driven in accordance with rpm) is likewise supposed to vary with the rpm of the engine. The genuine detection of rpm by the use of flyweights is therefore not effected in this known apparatus.
In the hydraulic regulator of U.S. Pat. No. 3 718 127, an rpm-dependent control pressure is generated by a separate modulation valve device, which is driven by rpm; this control pressure is transmitted to a posterior face of a piston, the control movement of which is exerted via a lever upon the metering device of a fuel injection pump.
Finally, the regulator device according to German Auslegeschrift No. 1 805 276 contains a regulator disposed in a connecting line between a high-pressure pump and a low-pressure pump; the regulator operates under the influence of centrifugal forces dependent on engine rpm and is embodied as a pressure medium control slide, having annular grooves for opening and closing pressure medium conduits. As a result, an adjusting device including a piston is triggerable such that an rpm-dependent regulation of the instant of injection is attained.